TWI814962B - ceramic heater - Google Patents

Abstract

The ceramic heater 10 includes a ceramic plate 20 with built-in inner and outer resistance heating elements 22 and 24, and a cylindrical shaft 40 connected to the back surface 20b of the ceramic plate 20. The elliptical hole 26 is provided in a direction deviating from the diameter direction of the ceramic plate 20 , from the starting point S of the inner axis area 20 d to the end position E of the outer peripheral portion of the ceramic plate 20 . The portion of the oval hole 26 that passes through the inner shaft region 20d becomes an elongated groove 26a. The terminals 22a, 22b, 24a, and 24b of each of the resistance heating elements 22 and 24 are centrally provided in the first divided area with the larger area among the two divided areas divided by the axis of the long groove 26a in the inner shaft area 20d.

Description

ceramic heater

The present invention relates to a ceramic heater.

Conventionally, a so-called 2-zone heater has been known as a ceramic heater in which resistance heating elements are independently embedded in the inner periphery of a disc-shaped ceramic plate having a wafer mounting surface. side and peripheral side. For example, Patent Document 1 discloses a ceramic heater 410 having a shaft as shown in FIG. 10 . This ceramic heater 410 having a shaft measures the temperature on the outer peripheral side of the ceramic plate 420 by using the outer peripheral side thermocouple 450 . The thermocouple guide 432 is a cylindrical member that extends straight from the bottom to the top inside the straight axis 440 and is then bent into an arc shape to perform a 90° direction change. The thermocouple guide 432 is installed in the slit 426 a , which is provided in the area surrounded by the straight axis 440 on the back side of the ceramic plate 420 . The slit 426 a forms an entrance portion of the thermocouple passage 426 , and is provided in a region (inner region of the direct axis) surrounded by the straight axis 440 on the back surface of the ceramic plate 420 in a direction deviating from the diameter direction of the ceramic plate 420 . The outer peripheral side thermocouple 450 is inserted into the barrel of the thermocouple guide 432 and reaches the end position of the thermocouple passage 426 . [Prior patent documents] [Patent Document]

[Patent Document 1] International Publication No. 2012/039453 Pamphlet (Figure 11)

[Problem to be solved by the invention]

However, in the ceramic heater 410, since the inner area of the shaft is divided into two divided areas with substantially equal areas by the slit 426a, if a plurality of terminals are to be arranged intensively in one of the divided areas, the degree of freedom of arrangement will be reduced. restricted.

The present invention was developed to solve this problem, and its main purpose is to increase the freedom of arrangement of a plurality of terminals in a multi-zone heater by centrally arranging them. [Means to solve the problem]

The ceramic heater of the present invention is: include: The disc-shaped ceramic plate has a wafer mounting surface; The cylindrical shaft is bonded to the back surface of the ceramic plate on the opposite side to the wafer mounting surface; The resistance heating element on the inner peripheral side is buried in the inner peripheral part of the ceramic plate; The outer peripheral side resistance heating element is buried in the outer peripheral part of the ceramic plate; The inner area of the shaft is the inside of the cylindrical shaft on the back side of the ceramic plate; An elliptical hole is provided along a direction deviating from the diameter direction of the ceramic plate, and from the inner area of the axis to a predetermined position on the outer periphery of the ceramic plate; and The accessory component is provided in the inner area of the shaft and includes a pair of terminals of the inner peripheral side resistance heating element and a pair of terminals of the outer peripheral side resistance heating element; The portion of the oval hole that passes through the inner area of the shaft becomes a long slot; The accessory components are centrally provided in the larger divided area of the two divided areas divided by the axis of the long groove in the inner shaft area.

In this ceramic heater, an additional element including a pair of terminals of the inner peripheral side resistance heating element and a pair of terminals of the outer peripheral side resistance heating element is provided in the inner shaft area of the back surface of the ceramic plate. The elliptical holes are arranged in a direction deviating from the diameter direction of the ceramic plate, and from the inner area of the shaft to a predetermined position on the outer periphery of the ceramic plate. The portion of the oval hole that passes through the inner area of the shaft becomes a long slot. The two divided areas within the axis are divided by the axis of the long groove (a straight line that is the same as the axis of the oval hole and deviates from the diameter direction of the ceramic plate). Therefore, one of the two divided regions has a larger area than the other. Here, the accessory components are concentrated in divided areas with a relatively large area. Therefore, in a multi-zone heater, it is possible to increase the degree of freedom of arrangement by centrally arranging additional components including a plurality of terminals. In addition, by centrally arranging the accessory components, wiring from the accessory components to external devices can be easily bundled.

In the ceramic heater of the present invention, the attached element may be configured such that the terminals of the inner and outer resistance heating elements are surrounded by the terminals of the inner and outer resistance heating elements. Region does not exist. Furthermore, each of the accessory components may be arranged at a position where electrical insulation can be maintained. Since the accessory components are concentrated in divided areas with a relatively large area, a plurality of terminals included in the accessory components can be easily arranged at positions where electrical insulation can be maintained.

In the ceramic heater of the present invention, the oval hole may be an oval hole for inserting a thermocouple into the thermocouple. In this way, the oval hole is used to insert the thermocouple.

In the ceramic heater of the present invention, the long groove may be used as a cylindrical thermocouple guide having a curved portion that converts the vertical direction to the horizontal direction with respect to the wafer mounting surface. In this way, in a multi-zone heater that can be installed with thermocouple conductors, the degree of freedom in its arrangement can be increased by centrally arranging a plurality of terminals.

In addition, "vertical" includes not only the case of being completely vertical but also the case of being substantially vertical (for example, the case of being within the tolerance range, etc.). The same goes for "level".

In the ceramic heater of the present invention, the length of the long groove may be determined to be longer than the length of the head end of the long groove in the bent portion of the thermocouple guide. In this manner, the thermocouple leads can be set more easily.

In the ceramic heater of the present invention, the outer diameter of the bent portion of the thermocouple guide may be smaller than the outer diameter of the vertical portion. In this way, the width of the long slot can be narrowed.

The ceramic heater of the present invention may also have the thermocouple guide arranged in the long slot, and further may have a thermocouple inserted into the thermocouple guide and the oval hole. When the thermocouple is provided, the temperature measuring portion of the thermocouple may be disposed within the width of the outer peripheral side resistance heating element when the ceramic plate is viewed from the back. In this way, the temperature change of the outer peripheral side resistance heating element can be detected with high speed response by the temperature measuring part of the outer peripheral side thermocouple.

In the ceramic heater of the present invention, the distance between the long groove and the accessory element may be 2 mm or more. In this way, it is possible to prevent cracks in the ceramic plate due to the narrow gap between the long groove and the attached components.

Preferred embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a perspective view of the ceramic heater 10, Figure 2 is a cross-sectional view along line A-A in Figure 1, Figure 3 is a cross-sectional view along line B-B in Figure 1, Figure 4 is a front view of the thermocouple guide 32, and Figure 5 is a diagram. An enlarged view of the central part of 3.

The ceramic heater 10 is used to heat the wafer W that is subjected to processing such as etching or CVD, and is installed in a vacuum chamber (not shown). This ceramic heater 10 includes: a disc-shaped ceramic plate 20 having a wafer mounting surface 20a; and a cylindrical shaft 40 having a surface (back surface) of the ceramic plate 20 opposite to the wafer mounting surface 20a. 20b joint.

The ceramic plate 20 is a disc-shaped plate made of a ceramic material such as aluminum nitride or aluminum oxide. The diameter of the ceramic plate 20 is not particularly limited, but is about 300 mm, for example. The ceramic plate 20 is divided into a small circular inner peripheral area Z1 and an annular outer peripheral area Z2 by a virtual boundary 20c (see FIG. 3 ) that is concentric with the ceramic plate 20 . The inner peripheral side resistance heating element 22 is embedded in the inner peripheral side area Z1 of the ceramic plate 20, and the outer peripheral side resistance heating element 24 is embedded in the outer peripheral side area Z2. The two resistance heating elements 22 and 24 are composed of coils whose main components are molybdenum, tungsten or tungsten carbide, for example. The ceramic plate 20 is produced by surface-bonding an upper side plate P1 and a lower side plate P2 that is thinner than the upper side plate P1 as shown in FIG. 2 .

The cylindrical shaft 40 is made of ceramic such as aluminum nitride or aluminum oxide, just like the ceramic plate 20 . The upper end of the cylindrical shaft 40 is diffusion bonded to the ceramic plate 20 .

The inner circumferential side resistance heating element 22 is formed as follows, as shown in Fig. 3. It starts from one of the pair of terminals 22a and 22b and is folded in a plurality of folded portions in a one-stroke manner. After almost the entire area of the peripheral area Z1, it reaches the other side of the pair of terminals 22a and 22b. The pair of terminals 22a and 22b are provided in a region (inner shaft region) 20d inside the cylindrical shaft 40 on the back surface 20b of the ceramic plate 20. Power supply rods 42a and 42b made of metal (for example, Ni) are joined to the pair of terminals 22a and 22b. In addition, the power supply rods 42a and 42b are inserted into an insulating tube (not shown).

The outer peripheral side resistance heating element 24 is formed as follows, as shown in Fig. 3. It starts from one of the pair of terminals 24a, 24b and is wired on the outer peripheral side while being folded back at a plurality of folded portions in a one-stroke manner. After almost the entire area of zone Z2, it reaches the other side of the pair of terminals 24a and 24b. The pair of terminals 24a and 24b are provided in the inner shaft area 20d of the back surface 20b of the ceramic plate 20. The power supply rods 44a and 44b made of metal (for example, Ni) are joined to the pair of terminals 24a and 24b. In addition, the power supply rods 44a and 44b are inserted into an insulating tube (not shown).

As shown in FIG. 2 , an oval hole 26 for inserting the outer peripheral side thermocouple 50 is provided inside the ceramic plate 20 parallel to the wafer mounting surface 20 a. The elliptical hole 26 is formed in the back surface 20b of the ceramic plate 20 from the starting point S of the inner axis region 20d to the end position E of the outer peripheral portion of the ceramic plate 20 in a direction deviating from the diameter direction of the ceramic plate 20. The portion of the oval hole 26 that passes through the inner shaft area 20d becomes a long slot 26a for arranging the head end of the bent portion 34 of the thermocouple guide 32. The long groove 26a opens into the inner space of the cylindrical shaft 40.

Here, the arrangement positions of the terminals 22a, 22b, 24a, and 24b will be described using FIG. 6 . The inner-axis area 20d is divided into first and second divided areas 20d1 and 20d2 by the axis L of the long groove 26a (a straight line that is the same as the axis of the oval hole 26 and deviates from the diameter direction of the ceramic plate 20). In FIG. 6 , the first divided area 20d1 is indicated by thick hatching, and the second divided area 20d2 is indicated by thin hatching. The area of the first divided region 20d1 is larger than the area of the second divided region 20d2. The terminals 22a, 22b, 24a, and 24b are collectively provided in the large first divided region 20d1 (excluding the long slot 26a). Furthermore, each of the terminals 22a, 22b, 24a, and 24b is arranged at a position where electrical insulation can be maintained.

As shown in FIG. 4 , the thermocouple guide 32 is a metal (for example, stainless steel) cylindrical member having a guide hole 32 a. The thermocouple guide 32 includes a vertical portion 33 extending in a vertical direction to the wafer mounting surface 20a, and a bent portion 34 that switches from the vertical direction to the horizontal direction. The outer diameter of the vertical portion 33 is larger than the outer diameter of the curved portion 34 , and the inner diameter of the vertical portion 33 is equal to the inner diameter of the curved portion 34 . In this manner, by making the outer diameter of the curved portion 34 smaller, the width of the long groove 26a inserted into the curved portion 34 can be narrowed. However, the outer diameter of the vertical portion 33 and the outer diameter of the curved portion 34 may be equal to each other. The curvature radius R of the curved portion 34 is not particularly limited, but is, for example, about 30 mm. The outer peripheral side thermocouple 50 is inserted into the guide hole 32a of the thermocouple guide 32 (see FIG. 2). The head end of the bent portion 34 can also be simply embedded in the long groove 26a, or can also be joined or bonded with the long groove 26a. In addition, the thermocouple conductor 32 may be formed of an electrically insulating material such as ceramics.

Inside the cylindrical shaft 40, as shown in FIG. 2, power supply rods 42a, 42b connected to each of the pair of terminals 22a, 22b of the inner peripheral side resistance heating element 22 or to the outer peripheral side resistance heating element 24 are arranged. Power supply rods 44a and 44b are connected to respective terminals of a pair of terminals 24a and 24b. Also disposed inside the cylindrical shaft 40 is an inner peripheral thermocouple 48 for measuring the temperature near the center of the ceramic plate 20 or an outer peripheral thermocouple 50 for measuring the temperature near the outer periphery of the ceramic plate 20 . The inner peripheral side thermocouple 48 is inserted into the recessed portion 49 provided on the back surface 20b of the ceramic plate 20, and the temperature measuring portion 48a at the head end is in contact with the ceramic plate 20. The recessed portion 49 is provided at a position that does not interfere with the respective terminals 22a, 22b, 24a, 24b or the long groove 26a. The outer peripheral side thermocouple 50 is a sheathed thermocouple. After passing through the guide hole 32a of the thermocouple guide 32 and the oval hole 26, the temperature measuring part 50a at the head end reaches the end position E of the oval hole 26.

Next, a usage example of the ceramic heater 10 will be described. First, the ceramic heater 10 is installed in a vacuum chamber (not shown), and the wafer W is placed on the wafer placement surface 20 a of the ceramic heater 10 . Next, the electric power supplied to the inner peripheral side resistance heating element 22 is adjusted so that the temperature detected by the inner peripheral side thermocouple 48 becomes a predetermined inner peripheral side target temperature, and the electric power supplied to the outer peripheral side resistance heating element 24 is adjusted. The temperature detected by the outer peripheral side thermocouple 50 becomes a predetermined outer peripheral side target temperature. Thereby, the temperature of the wafer W is controlled to a desired temperature. Then, the vacuum chamber is set to a vacuum environment or a reduced pressure environment, plasma is generated in the vacuum chamber, and the plasma is used to perform CVD film formation or etching on the wafer W.

In the ceramic heater 10 of this embodiment as described above, the first and second divided regions 20d1 and 20d2 are divided by the axis L of the long groove 26a (the same as the axis of the oval hole 26). The axis L is a straight line deviating from the diameter direction of the ceramic plate 20 . Therefore, the area of the first divided area 20d1 on one side is larger than that of the second divided area 20d2 on the other side. Here, the terminals 22a, 22b, 24a, and 24b are collectively provided in the first divided region 20d1 having a large area. Therefore, in a multi-zone heater to which the thermocouple lead 32 can be mounted, the accessory components including the plurality of terminals 22a, 22b, 24a, 24b can be centrally arranged, thereby increasing the degree of freedom of arrangement. In addition, by arranging the terminals 22a, 22b, 24a, and 24b in a centralized manner, wiring from the terminals 22a, 22b, 24a, and 24b to external devices can be easily bundled. In this case, additional components such as the inner peripheral side thermocouple 48 other than the terminals 22a, 22b, 24a, and 24b that supply power to the resistance heating elements 22 and 24 do not exist in the area surrounded by the terminals 22a, 22b, 24a, and 24b. .

In addition, when manufacturing the ceramic heater 10, the power supply rods 42a, 42b, 44a, 44b are connected to the terminals 22a, 22b, 24a, 24b exposed on the back surface 20b of the ceramic plate 20, and the cylindrical shape is used. In the case of the process of installing the thermocouple guide 32 after the shaft 40 is joined to the back surface 20b, the thermocouple guide 32 does not need to pass between the power supply rods, so the installation is easy.

Furthermore, since the incidental components of the terminals 22a, 22b, 24a, 24b, etc. are intensively provided in the first divided region 20d1 with a relatively large area, these incidental elements can be easily arranged at a position where electrical insulation can be maintained.

Furthermore, the length of the elongated slot 26 a which is the entrance portion of the oval hole 26 is determined to be longer than the length of the head end portion of the elongated slot 26 a in the bent portion 34 of the thermocouple guide 32 . Therefore, the thermocouple conductor 32 can be set more easily.

Furthermore, since the outer diameter of the bent portion 34 of the thermocouple guide 32 is made smaller than the outer diameter of the vertical portion 33, the width of the long groove 26a can be narrowed.

In addition, the present invention is not limited to the above-mentioned embodiments at all, and of course can be implemented in various forms as long as it falls within the technical scope of the present invention.

For example, in the above-described embodiment, the thermocouple guide 32 may be provided with a horizontal portion 35 as shown in FIG. 7 . The horizontal portion 35 is connected to the outlet of the bending portion 34 and faces the wafer mounting surface 20 a in the horizontal direction. extend. In this manner, the outer peripheral side thermocouple 50 can be guided to the oval hole 26 more smoothly. In addition, the portion of the thermocouple guide 32 having such a horizontal portion 35 arranged in the long groove 26a becomes longer. Therefore, it is preferable to set the length of the long groove 26a accordingly.

In the above-described embodiment, the temperature measuring portion 50a of the outer peripheral side thermocouple 50 in the oval hole 26 may be arranged so as to be as wide as the width of the outer peripheral side resistance heating element 24 when viewed from the back surface 20b (that is, as shown in FIG. 8 Within the width of the coil w). When the outer peripheral side resistance heating element 24 is not in the shape of a coil but in the shape of a ribbon (elongated flat plate), it may be arranged within the width of the ribbon. In this way, the temperature change of the outer peripheral side resistance heating element 24 can be detected with a high-speed response by the temperature measuring portion 50a of the outer peripheral side thermocouple 50.

In the above-mentioned embodiment, the two resistance heating elements 22 and 24 are in the shape of coils, but they are not It is specifically limited to a coil shape, and may also be a printed pattern, a ribbon shape, a mesh shape, etc., for example.

In the above-described embodiment, the ceramic plate 20 may have not only the resistance heating elements 22 and 24 built-in, but also an electrostatic electrode or an RF electrode. When the electrostatic electrode is built-in, a terminal of the electrostatic electrode (one of the accessory components) is provided in the first divided area 20d1 of the ceramic plate 20. When the RF electrode is built-in, a terminal of the RF electrode (one of the attached components) is provided in the first divided region 20d1 of the ceramic plate 20.

In the above-described embodiment, the length of the thermocouple guide 32 in the vertical direction is substantially equal to the height of the cylindrical shaft 40 . However, it may be shorter or longer than the height of the cylindrical shaft 40 .

In the above-mentioned embodiment, the inner peripheral zone Z1 may be divided into a plurality of inner peripheral sub-districts, and resistance heating elements may be arranged in each inner peripheral side sub-district in a one-stroke manner. Alternatively, the outer peripheral area Z2 may be divided into a plurality of outer peripheral subdivisions, and resistance heating elements may be arranged in each outer peripheral subdivision in a one-stroke manner. The number of terminals increases according to the number of cells. However, since these terminals are concentrated in the first divided area 20d1 with a relatively large area, it is easier to arrange even if the number of terminals increases.

In the above embodiment, the power supply rods 42a, 42b, 44a, and 44b are connected to the terminals 22a, 22b, 24a, and 24b of the ceramic plate 20, and the cylindrical shaft 40 is connected to the back surface 20b of the ceramic plate 20. After joining, the thermocouple guide 32 is installed, but the installation process is not limited to this. For example, after the cylindrical shaft 40 is joined to the back surface 20b of the ceramic plate 20 and the thermocouple lead 32 is installed, the power supply rods 42a, 42b, 44a, 44b and the terminals 22a, 22b, 24a, 24b can also be connected. Engagement.

In the above-mentioned embodiment, as shown in FIG. 9 , the distance G between the long groove 26a and the accompanying components (terminals 22a, 22b, 24a, 24b or recessed portion 49) is preferably 2 mm or more. In this manner, it is possible to prevent cracks from occurring in the ceramic plate 20 due to excessive narrowness between the long groove 26a and the accompanying components.

This patent application uses Japanese Patent Application No. 2018-238225 filed on December 20, 2018 as the basis for claiming priority, and the entire contents thereof are incorporated by reference in this patent specification. [Industrial Applicability]

The present invention is applicable, for example, as a member for a semiconductor manufacturing apparatus used to process a wafer.

10:Ceramic heater 20:ceramic plate 20a: Wafer mounting surface 20b: Back 20c: virtual border 20d: Inner axis area 20d1: 1st divided area 20d2: The second divided area 22: Inner peripheral side resistance heating element 22a,22b: terminal 24: Peripheral side resistance heating element 24a,24b: terminal 26:Oval hole 26a: long slot 32: Thermocouple guide 32a: Guide hole 33: Vertical part 34:Bending part 35: Horizontal part 40:Tubular shaft 42a, 42b, 44a, 44b: power supply rod 48: Inner peripheral side thermocouple 48a: Thermometry Department 49: concave part 50: Peripheral side thermocouple 50a: Thermometry Department 410:Ceramic heater 420:Ceramic plate 426: Thermocouple path 426a: slit 432: Thermocouple guide 440: Straight shaft 450: Peripheral side thermocouple L: axis P1: Upper side panel P2: Lower side panel S: starting point E:Terminal position W:wafer Z1: Inner peripheral area Z2: Peripheral side area

[Fig. 1] is a perspective view of the ceramic heater 10. [Fig. 2] is a cross-sectional view of A-A in Fig. 1. [Figure 3] is a cross-sectional view of B-B in Figure 1. [Fig. 4] This is a front view of the thermocouple guide 32. [Figure 5] is an enlarged view of the center part of Figure 3. [Fig. 6] It is an explanatory diagram of the arrangement positions of terminals 22a, 22b, 24a, and 24b. [Fig. 7] is a front view of another example of the thermocouple guide 32. [Fig. 8] This is an explanatory diagram showing an example of the position of the temperature measuring portion 50a of the outer peripheral side thermocouple 50. [Fig. 9] This is an explanatory diagram showing the distance G between the long groove 26a and the accompanying components. [Figure 10] An explanatory diagram of a conventional example.

10:Ceramic heater

20:ceramic plate

20a: Wafer mounting surface

20b: Back

20d: Inner axis area

22: Inner peripheral side resistance heating element

22a,22b: terminal

24: Peripheral side resistance heating element

24a,24b: terminal

26:Oval hole

26a: long groove

E:Terminal position

S: starting point

32: Thermocouple guide

32a: Guide hole

33: Vertical part

34:Bending part

40:Tubular shaft

42a, 42b, 44a, 44b: power supply rod

48: Inner peripheral side thermocouple

48a: Thermometry Department

49: concave part

50: Peripheral side thermocouple

50a: Thermometry Department

P1: Upper side panel

P2: Lower side panel

W:wafer

Z1: Inner peripheral area

Z2: Peripheral side area

Claims (10)

A ceramic heater, including: a disc-shaped ceramic plate having a wafer mounting surface; a cylindrical shaft connected to the back surface of the ceramic plate opposite to the wafer mounting surface; and an inner peripheral side resistor The heating element is embedded in the inner peripheral part of the ceramic plate; the outer peripheral side resistance heating element is embedded in the outer peripheral part of the ceramic plate; the inner shaft area is the inner side of the cylindrical shaft on the back side of the ceramic plate ; The oval hole is provided in a direction deviating from the diameter direction of the ceramic plate, and is located at a predetermined position from the inner area of the shaft to the outer circumference of the ceramic plate; and the accessory component is provided in the inner area of the shaft, It also includes a pair of terminals of the inner peripheral side resistance heating element and a pair of terminals of the outer peripheral side resistance heating element; the part of the oval hole that passes through the inner area of the shaft becomes a long slot; the accessory components are centrally arranged The larger of the two divided areas divided by the axis of the long groove in the inner area of the axis. For example, the ceramic heater of claim 1 of the patent scope, wherein in the attached component, other than the terminals of the inner peripheral side and the outer peripheral side resistance heating element are connected to the terminals of the inner peripheral side and the outer peripheral side resistance heating element. The enclosed area does not exist. For example, in the ceramic heater of claim 1, the oval hole is an oval hole for inserting a thermocouple. For example, the ceramic heater according to any one of the patent claims 1 to 3, wherein the long groove is for arranging a cylindrical heat sink having a curved portion that converts the wafer mounting surface from a vertical direction to a horizontal direction. Used for galvanic conductors. For example, in the ceramic heater of claim 4, the length of the long slot is determined to be longer than the length of the head end of the long slot in the bent portion of the thermocouple conductor. For example, in the ceramic heater of item 5 of the patent application, the thermocouple guide further includes a vertical portion extending in the vertical direction to the wafer mounting surface, and the outer edge of the curved portion of the thermocouple guide is The diameter system is smaller than the outer diameter of the vertical portion. For example, the ceramic heater of claim 4 includes the thermocouple conductor arranged in the long slot. For example, the ceramic heater of item 7 of the patent application includes a thermocouple inserted into the thermocouple guide and the oval hole. For example, in the ceramic heater of claim 8, when the ceramic plate is viewed from the back, the temperature measuring portion of the thermocouple is disposed within the width of the resistance heating element on the outer peripheral side. For example, if the ceramic heater is applied for any one of items 1 to 3 of the patent scope, the distance between the long slot and the attached component is more than 2mm.

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